Work-positioning grinding fixture

ABSTRACT

A grinding fixture includes a base and a work support assembly including a rotary shaft mounted on the base to swing from side to side transverse to the axis of the shaft. A work holder on the end of the shaft releasably grips the work and radial relief grind structure includes a circular index plate rotatable relative to the shaft having a peripheral cam slot with an eccentric cam surface which slidably engages a cam follower pin for radial relief grinding. Circumferentially spaced index holes in the plate and an index pin establish selected angular increments of rotational movement. A locking slot in the index plate cooperates with the same cam follower pin for locking the shaft against rotational movement for other grinding procedures.

United States Patent Dunkin [4 1 Aug. 15, 1972 [54] WORK-POSITIONING GRINDING FOREIGN PATENTS OR APPLICATIONS FIXTURE 57,348 8/1911 Switzerland ..s1/22s 72 Inventor; u Dunkin, 35 g Amherst, 562,057 6/1944 Great Britain ..5l/225 glewood,Colo. 80110 P Ex H Id D W h d rzmary ammeraro te ea [22] Flled. NOV. 4, 1970 Au0rney Rei"y and Lewis [21] Appl. No.: 86,891

[57] ABSTRACT [52 us. Cl ..s1/121, 51/225 A grinding fixture includes a base and a work Support 51 Int. Cl. ..B24b 3/22 assemblyfmcluqlgg a "23W shaft moumeg F 5 Fi ld fsearchnmsl 219 225 234 21 97 1O sw1ng rom S1 e 10 81 e transverse 10 t 6 axis 0 1 e 1 e o I PC shaft. A work holder on the end of the shaft releasably [56] References Cited grips the work and radial relief grind structure includes a circular index plate rotatable relative to the UNITED STATES PATENTS shaft having a peripheral cam slot with afn eccentric cam surface whic s idably engages a cam ollower pin 2'406'l34 3 31 Ei f for radial relief grinding. Circumferentially spaced 2391317 1 ll cm 4x index holes in the plate and an index pin establish 23491459 9/1948 Eckert 3 selected angular increments of rotational movement. Smdler "51/219 PC A locking slot in the index plate cooperates with the Moody ..5 1/225 same cam follower pin for locking the shaft against rotational movement for other grinding procedures.

13 Claims, 7 Drawing Figures Patented Aug. 15, 1972 FIG.4

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FIG.7

WORK-POSITIONING GRINDING FIXTURE This invention relates to devices for positioning the work for grinding surfaces thereof and more particularly to a novel and improved fixture for use in grinding a variety of types of work in an accurate and efficient manner.

A number of grinding fixtures have heretofore been provided for holding work in position to be ground by a grinding wheel. Their use makes possible a more accurate and rapid grinding with a corresponding reduction of cost. Generally, prior art fixtures have been mechanically complex and somewhat difficult to operate with a corresponding relatively high cost of manufacture.

Accordingly, it is an object of this invention to provide a relatively simple, reliable, and easy to operate grinding fixture suitable for use in accurately grinding a wide variety of types of work.

Another object of this invention is to provide an improved work-positioning grinding fixture which is suitable for use in grinding surfaces on a wide variety of tools including taps, reamers, punches and the like as well as for radius dressing of grinding wheels and the grinding of engine valves.

A further object of this invention is to provide a work-positioning grinding fixture suitable for making a number of radial relief grinds in machinists tools such as taps.

Yet a further object of this invention is to provide a novel and improved grinding fixture characterized by combined rotational movement and lateral swinging or rocking movement in a direction transverseto the rotational movement.

Still another object of this invention is to provide a novel and improved grinding fixture in which an index plate is carried on the rotary support shaft which cooperates with a cam follower pin to provide for radial relief grinding.

In accordance with the present invention in the preferred embodiment shown, there is provided a base and a work support assembly mounted on the base including a rotary shaft joumaled in a support housing with the housing being swingably mounted on the base to rock about a point below the shaft for a lateral rocking movement from side to side between a work inspection position on one side and a work grinding position on the other side. A work holder mounted on the front end of the shaft releasably grips the work and locates it relative to the shaft An index plate on the shaft has an elongated slot with an eccentric cam surface which bears against a cam follower pin arranged parallel to the axis of the shafi and disposed on one side of the shaft to establish an eccentric pattern of rotational movement as the cam surface rotates over the follower pin for radial relief grinding. Circumferentially spaced holes in the index plate and an index pin mounted on the shaft establish selected angular increments for the shaft. A lock slot in the index plate cooperates with the cam follower pin to lock the shaft against rotation.

Other objects, advantages and capabilities of the present invention will become more apparent as the description proceeds taken in conjunction with the accompanying drawings in which:

FIG. 1 is a side elevation view of a grinding fixture embodying features of the present invention set in the work grinding position;

FIG. 2 is a top plan view of the fixture shown in FIG. 1

. FIG. 3 is a sectional view taken along lines 3-3 of FIG. 2;

FIG. 4 is a rear end elevation view of the fixture shown in FIG. 1 with the inspection position shown in dashed lines;

FIG. 5 is a front end elevation view of the fixture shown in FIG. .1 in the inspection position with the V- block vertical and a tap being mounted thereon;

FIG. 6 is a fragmentary elevation view showing the relative position of a grinding wheel in relation to the tool; and

FIG. 7 is an alternate form of work holder for use in the grinding fixture in place of the V-block device shown in FIGS. 1-6. I

Referring now to the drawings, the fixture shown, in general, comprises a mounting base 11 with a flat bottom surface, a movable work support assembly 12 mounted on the base in such a way as to provide for both rotational movement and lateral swinging movement transversely to the axis of rotation, together with an adjustable cross-feed mechanism 14 mounted on the base to one side of the movable work support assembly 12 which provides for selective lateral positioning of the work support assembly relative to the face of the grinding wheel 15 shown in FIG. 6 and described more fully' hereinafter. The term wor as used herein is intended to refer to a variety of parts, usually cylindrical, such as taps, reamers, punches for die making, single point tools and the like. In addition the fixture may be used to radius-dress grinding wheels and grind engine valves.

The base 11 has elongated spaced parallel slots 17 adapted to be mounted and secured to a flat table (not shown) adjacent the grinding wheel 15. This adjustment for the base permits the positioning of the work at a selected charnfer angle designated A in FIG. 6 relative to the flat grinding face 15a of the grinding wheel. The charnfer angle forv the work is then adjustable to a selected angle by loosening fastener bolts (not shown) which may secure the base plate to the table and slide it in a horizontal plane relative to the vertically disposed grinding face 15a. The base 11 is also provided with a pair of upstanding support members 18 and 19 spaced longitudinally of the base for supporting the movable work support assembly 12 described hereinafter.

The movable work support assembly 11 includes a spindle or shaft 21 rotatably mounted in a tubular housing 22 for rotation of the shaft about a generally horizontal axis above the base. The shaft 21 is supported in the housing 22 in a pair of sleeve bearings 24 and 25 which are inserted into the opposite ends of the housing and have flanged end portions 26 and 27, respectively, the flanged end portions of each butting against the ends of the housing. Spacer washers 28 and 29 are provided on each side of the flanged end portions of the sleeve bearings.

The housing 22 has a pair of end rocker plates 31 and 32 at its opposite ends and the plates include depending leg portions 33 and 34, respectively, which project downwardly from the ends of the housing. These leg portions are connected by a horizontal pivot member 35 to the adjacent upstanding support member on the base as seen in FIG. 3. One side of the leg portion has a curved section 37 and the other has a flat section 38 which engages the base 11 to hold the work assembly in the inspection position C. In this way the movable work support assembly including the rotary shaft will pivot about a point below the axis of the shaft and swing or rock the shaft from side to side in a direction transverse to its rotational axis to position it in a direction transversely to the face of the grinding wheel. The work assembly is shown to swing between a grinding position designated B on one side of the pivot and an inspection position designated C on the other side of the pivot member 35. This rocking support structure is arranged so that in the upright position it is generally symmetrically arranged with respect to a vertical line through its pivot established by member 35 and swings through an are on each side of the vertical line through the pivot point.

A V-block-type holder device 41 is mounted on the front end of the shaft and includes a flange member 42 fixedly secured to the front end of the shaft 21, a backing plate 43 fixedly secured on the forward face of the flange member 42 by bolts 40. Backing plate 43 has a forwardly extending flange portion 430 at its lower end, and a pair of side plates 44 and 45 are secured to the front face of the backing plate by cap screws 46. The bottom edge of the side plates 44 and 45 abuts against flange portion 430. The side plates 44 and 45 have a beveled inner edge and slidably receive a slide plate 48 having beveled outer edges to provide a guided movement for the slide plate. The slide plate 48 in turn supports a V-block 49 made of a solid block of material with a V-shaped upper support surface 49a for the sup port of work such as the tap 50 shown in FIG. 4. An adjustment screw 51 having a knurled head extends through a vertical hole in the bottom flange portion 43a and threads into an internally threaded hole in the side plate 48. A collar 52 is mounted on the screw thread to hold it on the flange portion so that a threading of the screw 51 adjusts the slide plate 48 up and down between the side plates to adjust the V-block 49 up and down. This adjustment permits the V-block to be moved off-center from the center of the shaft to provide for an offset grind in the work. A generally C- shaped clamp member 53 is mounted on the V-block to clamp the tap 50 against its V-shaped support surface 494 and clamp member 53 includes an upper bight portion joining a pair of spaced parallel legs which extend along the sides of the V-block 49 and having intumed lower end portions 530 which extend into notches in the side of the V-block. An adjustment screw 55 then threads through the bight portion and down against the work, as best seen in FIG. 4, to locate the work in a centered position and hold it firmly in place. This V- block and clamp arrangement disposes a cylindrical work part along a perpendicular line through the axis of the shaft. The tool is located either in a centered concentric position or an offset position by means of a dial indicator prior to grinding. This adjustment is provided by turning screw 51.

A support hub 61 carrying an index plate 62 releasably slides over the rear end of the shaft 21 and is fixedly secured thereto for conjoint rotation therewith. The support hub 61 has a relatively thin inner annular support flange portion 64 providing a seat or surface on which the indexing plate will rotate and an inner washer 65 is secured to the inner end of the flange to hold the index plate in place with a minimum of axial play. An enlarged intermediate portion 66 of the support hub carries hollow grip base 67. Base 67 has an externally threaded end portion which threads into an internally threaded hole in portion 66 which in turn supports a slidable index pin 68 terminating in a head 68a. The pin is positioned in a bore in the base 67 at a selected radial distance from the center of the shaft. The hub 61 has an outer flange portion 69 which receives a set screw 71 for afiixing the hub to shaft 21 for conjoint rotation therewith.

The index plate 62 is a generally flat circular disc and has one group of indexing holes designated 72 with centers arranged circumferentially at 90 intervals and they align with the index pin so if the index pin is inserted into a selected one of holes 72 the index plate will conjointly rotate with the shaft. The index plate 62 is also provided with a second group of index holes designated 73 which are disposed outwardly from the first group and have their centers arranged at 60 intervals. The hub portion 66 is shown as having another internally threaded aperture 74 to which hollow base 67 may be threaded so that the index pin 68 will releasably insert into a selected hole of the second group of holes to index the shaft for 60 of rotation.

An elongated cam slot 75 is provided in the periphery of the cam plate. This slot spans approximately a 90 segment of its circumference. The cam slot has an eccentric cam surface 75a providing radial edges at each end to limit rotation. One limit of the cam slot 75 is made adjustable to smaller segments by the provision of an arcuate slotted member 76 which is secured to the side of the plate by screws 77 and is movable along the circumference of the plate to provide an adjustable limit or stop for the eccentric cam slot. A lock slot 78 only slightly wider than the cam follower pin is also provided in the index plate.

The cross-feed mechanism 14 which cooperates with the above described index plate includes a base plate 81 mounted on the main base 11 and extending at right angles thereto, the base plate 81 having an upright support portion 82 along one side edge. A lever 83 is pivotally mounted on the upright portion 82 by a pivot member 84 extending through apertures in the lever and upright support 82 so that the lever pivots in a vertical plane toward and away from the work holder assembly 11. A cam follower pin 85 is mounted on and projects at right angles to lever 83 so as to swing toward and away from the index plate in a parallel relation to its axis of rotation. An adjustable stop screw 86 is threaded into an upstanding support arm 87 and its inner end bears against the outer edge of the crosslever to adjust the lateral position index pin and thereby limit the swing of the work support assembly in the grinding position. A head 86a on the screw is provided with micrometer markings for use in establishing a particular depth of grind. It is noted that the distance between the pivot point of the lever 83 and the center of the cam follower pin designated r1 in FIG. 3 is the same as the distance between the pivot for the work support assembly and the axis of rotation of the shaft designated r2 in FIG. 3.

OPERATION In a full sequence of operation, the base 11 is first positioned on a support table and clamped or fastened at a selected chamfer angle designated A using a protractor to set the angle. In the grinding of a relief grind surface, as for example sharpening of the two cutting edges of tap 50 shown, the work support as sembly 12 is swung to the grinding position B and the shaft is rotated counterclockwise as viewed in FIG. 4 with the eccentric surface 75a engaging the cam follower pin 85 until the pin engages the end of the slot. The index pin 68 is then inserted into a selected index hole 72. The tap 50 is then clamped in the V-block and the tap is positioned so that its cutting edge will contact the grinding wheel with the cutting edge disposed in a horizontal plane as shown. The adjustable stop screw 86 is then adjusted to bring the tap into a light contact with the grinding wheel. Next, shaft 21 is rotated within the limits established by the ends of the eccentric cam slot 75. The work supporting assembly 12 is then swung away from the wheel to the inspection position C and the index pin 18 is retracted and inserted into the next selected index hole to grind the next edge. The next selected index hole will be at 180 to the first for a twoflute tap. The work support assembly 11 is then swung back until the eccentric cam slot surface contacts the follower pin 85 and the shaft is again rotated between the limits established by the slot sides.

The lock slot 78 is used for grinding both cylindrical parts and making both concentric and eccentric cylindrical surface grinds. In a full series of operation for the grinding procedure the index pin 68 is withdrawn so that the shaft 21 rotates freely. The shaft is first set in the inspection position C and the work loaded into position in the V-block. A dial indicator is used to check to see if the work is concentric or eccentric relative to the shaft axis as required. The work support assembly 12 is then swung back so that the lock slot 78 engages the cam follower pin 85. The adjustable stop screw 86 is then adjusted again so that the work contacts the grinding wheel lightly. The shaft is then rotated by hand, usually by'gripping base 67, and then the support assembly is swung out to the inspection position C. The work is checked with a micrometer to see if it has been reduced sufiiciently in size. This is repeated until the desired diameter is achieved.

For the grinding of geometric shapes such as triangular, hexagonal and square shapes, and combined rounds and flats after the base has been clamped to the support table, the work support assembly is moved to the inspection position C. The work is loaded and the dial indicator is used to establish the concentric center. The work support assembly is then swung back into the grinding position and the work is ground to the desired diameter as above described. The work support assembly is then swung out and the index pin 68 is inserted into the desired index hole and is swung back into the lock slot. The adjustable stop screw 86 is set to the required depth of flat, the grinding is accomplished and the work support assembly is swung out to the inspection position and indexed for grinding of the next flat. The first group of holes designated 72 are suitable for making twoand four-sided shapes and the second group of holes 73 are suitable for making threeand six-sided shapes, thereby giving both simplicity and substantial flexibility to the index mechanism. Again the second group of holes 73 are utilized simply by removing base 67 from its position shown and threading it into aperture 74.

An alternative arrangement for the V-block device 41 is shown in FIG. 7. This arrangement is an extension 91 of the shaft 21 which terminates in a cylindrical socket 92 having a radial aperture 93. A slip fit bushing 94 of a selected internal diameter releasably inserts into the socket 92 and the bushing is held in place by a set screw 95 which threads through aperture 93 and a radial aperture 96 in the bushing to hold the work in place at the end of the shaft. This arrangement does not have a radial adjustment for offset grinding but is considerably less expensive to manufacture than that of the V-block shown in FIG. 1-6.

Although the present invention has been described with a certain degree of particularity, it is understood that the present disclosure has been made by way of example and that changes in details of structure may be made without departing from the spirit thereof.

I claim:

1. A grinding fixture adapted for use with a grinding surface comprising a base, a work support assembly mounted on the base including a work holder supported for rotation about a horizontal axis and mounted on the base to swing from side to side transversely to the horizontal axis between an inspection position and a grinding position, an index plate mounted for rotation about said horizontal axis on said work support assembly, independently of the rotation of said work holder, said plate having a peripheral slot with an eccentric cam surface and limit edges at each end thereof, a cam follower pin mounted on said base on one side of said work support assembly and engageable with said cam surface between said limit edges for radial relief grinding of work positioned against the grinding surface, and means cooperating with said index plate to lock the index plate for rotation with said work holder about the horizontal axis and advance the work holder relative to the index plate in increments to establish preselected angular increments of rotation for said work holder for radial relief grinding a selected number or edges in the work.

2. A grinding fixture as set forth in claim 1 wherein said work support assembly is pivoted at its lower end on the base below said work holder.

3. A grinding fixture as set forth in claim 1 wherein one of the limit edges of said eccentric cam surface is adjustable relative to the other to establish a selected angular increment of rotation.

4. A grinding fixture as set forth in claim 3 wherein said shaft swings through an arc on each side of a vertical line through the pivot point on the base.

5. A grinding fixture as set forth in claim 1 wherein said cam follower pin is supported on a lever pivoted toward and away from said work support assembly, and adjustable means to position said lever to adjust the depth of the grind.

6. A grinding fixture as set forth in claim 5 wherein said adjustable means includes a screw thread terminating in a turning head marked with micrometer indicia on its periphery to indicate grinding depths.

7. A grinding fixture as set forth in claim 1 wherein said index plate is in the form of a generally circular disc and has a group of four circumferentially spaced index holes each spaced the same distance from the axis of rotation and a hub secured to the shaft carrying an index pin insertable into a selected index hole to lock the shaft to said index plate at one of four selected angular positions.

8. A grinding fixture as set forth in claim 7 wherein said index plate has a second group of six circumferentially spaced index holes each spaced the same distance from the axis of rotation and a different distance from the first-mentioned group of four holes for establishing six selected angular positions, said hub having an aperture alignable with said second group adapted for receiving an index pin.

9. A grinding fixture as set forth in claim 1 wherein said index plate has a peripheral locking slot for receiving said cam follower pin for locking the work holder against rotational movement.

10. A grinding fixture as set forth in claim 1 wherein said work holder includes a V-block and clamp assembly, the center of said V-block being adjustable radially of the horizontal axis of rotation for making offset grinds on the work.

11. A grinding fixture as set forth in claim 1 wherein said work holder includes a hollow rotary socket member having a radial aperture, a bushing of a selected internal diameter slidably insertable into said socket and having a radial aperture, and a set screw threading through said apertures.

12. A grinding fixture adapted for use with a grinding surface comprising:

a base,

a work support assembly mounted on said base including a shaft supported for rotation about a horizontal axis and a work holder supported on one end of the shaft for conjoint rotation therewith, said shaft being pivotally mounted for swinging movement from side to side transversely to the axis of rotation between an inspection position on one side of a vertical line through the pivot point for the shaft and a grinding position on the other side of the vertical line,

an index plate mounted for rotation relative to said shaft, said plate having an elongated peripheral slot with a cam surface eccentric to said horizontal axis, said cam surface having limit edges at each end thereof,

an index pin insertable into a selected of circumferentially spaced holes in the index plate to lock the index plate for rotation with said work holder and advance the work holder relative to the index plate in increments to establish selected angular increments of rotation for said shaft, and

a cam follower pin supported from said base and extending parallel to the shaft and engageable with the cam surface as the shaft and index plate is rotated between limits established by the pin engaging the limit edges at the ends of said slot for radial relief grinding a selected number of edges in the work.

13. In grinding apparatus including a grinding wheel having a grinding face and a support base adjacent the grinding wheel, the combination of a base adapted to mount on the support base and be secured at a selected chamfer angle relative to the i'i p j o st assembly mounted on said base including a tubular housing having depending leg portions pivotally mounted on the base to pivot from side to side of a vertical line through the center of the pivot, a shaft supported in the housing for rotation about a horizontal axis and a work holder supported on one end of the shaft for conjoint rotation therewith and swinging movement in a direction transverse to the horizontal axis of rotation,

generally circular index plate mounted to rotate about the horizontal axis relative to said shaft, said plate being disposed oppositely of the work holder and having first and second groups of circumferentially spaced index holes,

a hub secured to the rear end of the shaft and carrying an index pin arranged to releasably insert into selected of the first group of said index holes and adapted to selectively mount in the hub in alignment with the second group of holes, said plate having an elongated peripheral cam slot with an eccentric cam surface for establishing an eccentric pattern of rotational movement and a peripheral stop slot for locking the shaft against rotational movement, and

a cross-feed device mounted on the base at the side of said index plate including an upright pivotal lever, a cam follower pin mounted on the lever parallel to the axis of the shaft and selectively engageable with said peripheral cam and stop slots in said index plate in the grinding position, and an adjustable stop screw to advance and retract said lever and pin toward and away from said index circular plate to set the work supported assembly for a selected depth of grind. 

1. A grinding fixture adapted for use with a grinding surface comprising a base, a work support assembly mounted on the base including a work holder supported for rotation about a horizontal axis and mounted on the base to swing from side to side transversely to the horizontal axis between an inspection position and a grinding position, an index plate mounted for rotation about said horizontal axis on said work support assembly, independently of the rotation of said work holder, said plate having a peripheral slot with an eccentric cam surface and limit edges at each end thereof, a cam follower pin mounted on said base on one side of said work support asSembly and engageable with said cam surface between said limit edges for radial relief grinding of work positioned against the grinding surface, and means cooperating with said index plate to lock the index plate for rotation with said work holder about the horizontal axis and advance the work holder relative to the index plate in increments to establish preselected angular increments of rotation for said work holder for radial relief grinding a selected number or edges in the work.
 2. A grinding fixture as set forth in claim 1 wherein said work support assembly is pivoted at its lower end on the base below said work holder.
 3. A grinding fixture as set forth in claim 1 wherein one of the limit edges of said eccentric cam surface is adjustable relative to the other to establish a selected angular increment of rotation.
 4. A grinding fixture as set forth in claim 3 wherein said shaft swings through an arc on each side of a vertical line through the pivot point on the base.
 5. A grinding fixture as set forth in claim 1 wherein said cam follower pin is supported on a lever pivoted toward and away from said work support assembly, and adjustable means to position said lever to adjust the depth of the grind.
 6. A grinding fixture as set forth in claim 5 wherein said adjustable means includes a screw thread terminating in a turning head marked with micrometer indicia on its periphery to indicate grinding depths.
 7. A grinding fixture as set forth in claim 1 wherein said index plate is in the form of a generally circular disc and has a group of four circumferentially spaced index holes each spaced the same distance from the axis of rotation and a hub secured to the shaft carrying an index pin insertable into a selected index hole to lock the shaft to said index plate at one of four selected angular positions.
 8. A grinding fixture as set forth in claim 7 wherein said index plate has a second group of six circumferentially spaced index holes each spaced the same distance from the axis of rotation and a different distance from the first-mentioned group of four holes for establishing six selected angular positions, said hub having an aperture alignable with said second group adapted for receiving an index pin.
 9. A grinding fixture as set forth in claim 1 wherein said index plate has a peripheral locking slot for receiving said cam follower pin for locking the work holder against rotational movement.
 10. A grinding fixture as set forth in claim 1 wherein said work holder includes a V-block and clamp assembly, the center of said V-block being adjustable radially of the horizontal axis of rotation for making offset grinds on the work.
 11. A grinding fixture as set forth in claim 1 wherein said work holder includes a hollow rotary socket member having a radial aperture, a bushing of a selected internal diameter slidably insertable into said socket and having a radial aperture, and a set screw threading through said apertures.
 12. A grinding fixture adapted for use with a grinding surface comprising: a base, a work support assembly mounted on said base including a shaft supported for rotation about a horizontal axis and a work holder supported on one end of the shaft for conjoint rotation therewith, said shaft being pivotally mounted for swinging movement from side to side transversely to the axis of rotation between an inspection position on one side of a vertical line through the pivot point for the shaft and a grinding position on the other side of the vertical line, an index plate mounted for rotation relative to said shaft, said plate having an elongated peripheral slot with a cam surface eccentric to said horizontal axis, said cam surface having limit edges at each end thereof, an index pin insertable into a selected of circumferentially spaced holes in the index plate to lock the index plate for rotation with said work holder and advance the work holder relative to the index plate in increments to establish selected angular inCrements of rotation for said shaft, and a cam follower pin supported from said base and extending parallel to the shaft and engageable with the cam surface as the shaft and index plate is rotated between limits established by the pin engaging the limit edges at the ends of said slot for radial relief grinding a selected number of edges in the work.
 13. In grinding apparatus including a grinding wheel having a grinding face and a support base adjacent the grinding wheel, the combination of a base adapted to mount on the support base and be secured at a selected chamfer angle relative to the grinding face, a work support assembly mounted on said base including a tubular housing having depending leg portions pivotally mounted on the base to pivot from side to side of a vertical line through the center of the pivot, a shaft supported in the housing for rotation about a horizontal axis and a work holder supported on one end of the shaft for conjoint rotation therewith and swinging movement in a direction transverse to the horizontal axis of rotation, a generally circular index plate mounted to rotate about the horizontal axis relative to said shaft, said plate being disposed oppositely of the work holder and having first and second groups of circumferentially spaced index holes, a hub secured to the rear end of the shaft and carrying an index pin arranged to releasably insert into selected of the first group of said index holes and adapted to selectively mount in the hub in alignment with the second group of holes, said plate having an elongated peripheral cam slot with an eccentric cam surface for establishing an eccentric pattern of rotational movement and a peripheral stop slot for locking the shaft against rotational movement, and a cross-feed device mounted on the base at the side of said index plate including an upright pivotal lever, a cam follower pin mounted on the lever parallel to the axis of the shaft and selectively engageable with said peripheral cam and stop slots in said index plate in the grinding position, and an adjustable stop screw to advance and retract said lever and pin toward and away from said index circular plate to set the work supported assembly for a selected depth of grind. 